1. Field of the Invention
The present invention relates to a canned motor wherein a thin anticorrosive cylindrical liner or can is inserted inside a motor stator to insulate the stator from a liquid, and is particularly concerned with the structure of a stator chamber of the canned motor.
2. Prior Art
Shown in FIG. 2 is a prior art canned motor for use in a deep well pump. The canned motor is ready for mounting a pump body or load (not indicated) on an upper shaft end in the illustration. The motor includes a stator chamber constructed integrally by welding a stator core 101, a frame or outside can 102, an inside can 103, a load side (power cable extraction side) end plate 104 and a counter load side end plate 105, bearing brackets 106 and 107 mounted on a load side and a counter load side of the stator chamber respectively, a rotor 108 and a shaft 109 constituting a rotator, a lower thrust bearing 110 for supporting the rotator axially, and a thrust bearing case 111 for containing the thrust bearing 110 therein, wherein the inside can 103 mounted inside the stator is fitted in an inside peripheral portions of the load side and the counter load side end plates 104 and 105 respectively and welded thereto as shown by w in FIG. 2a.
A radial bearing 112 and a shaft seal 113 for sealing a liquid (pure water, etc.) enclosed in the motor from contact with an external fluid are mounted on the upper load side bearing bracket 106, and a suction casing of the pump (not indicated) is mounted on an upper portion of the bearing bracket 106. Further, a mounting area for a power cable 114 is provided on the load side end plate 104 of the stator chamber and the bearing bracket 106.
On the other hand, a diaphragm 115 for absorbing expansion and contraction corresponding to a change in temperature of a liquid enclosed in the motor is mounted on the lower portion of the thrust bearing case 111.
However, in the prior art canned motor described above, since the load side bearing bracket 106 and the counter load side bearing bracket 107 for mounting the bearings are provided on the load side end plate 104 and the counter load side end plate 105 of the stator chamber forming a stator assembly respectively, the following problems inevitably arise.
(i) The number of components for fabricating a motor is increased and, therefore, it is difficult to make the motor compact and an assembling of the motor is troublesome. PA0 (ii) While provision of sufficient space for connecting the cable 114 and a stator winding 101a is necessary within the stator chamber on the load side or the power cable extraction side, space in the stator chamber is limited by the provision of the end plate 104, and thus the stator chamber must be elongated axially so as to secure sufficient space for connecting the winding 101a and the power cable 114, and, therefore, a motor size is increased in an axial direction. PA0 (iii) Since the bearing brackets 106 and 107 are interposed on the load side and the counter load side of the stator assembly respectively, satisfactory heat radiation from the opposite ends of the stator chamber cannot be expected, and hence a cooling of the canned motor depends substantially on the radiation from an outer peripheral surface of the stator chamber only.